Use HTML in slidetext

Instead of checking the slide_text with check_plain()

// add slide_text variable
if (isset($result->node_data_field_pager_item_text_field_slide_text_value)) {
  $slider_items[$key1]['slide_text'] =  check_plain($result->node_data_field_pager_item_text_field_slide_text_value);
}

use check_markup()

// add slide_text variable
if (isset($result->node_data_field_pager_item_text_field_slide_text_value)) {
  $slider_items[$key1]['slide_text'] =  check_markup($result->node_data_field_pager_item_text_field_slide_text_value);
}